The US Senate will hold a crucial vote tomorrow, barring a last-minute compromise, on a proposal to ban filibusters of President George Bush's judicial nominations - and, many warn, change the nature of the upper chamber of Congress.
Under the rule change, described by many constitutional experts as a potential watershed in more than 200 years of Senate history, a simple majority of just 51 Senators would be required to end debate, instead of the current "super-majority" of 60.
The proposal relates only to judicial nominations, but minority Democrats charge that it is the thin end of a wedge that would ultimately end the filibuster in its entirety. Even in its present form however, the stakes could hardly be higher.
Tomorrow's expected test vote will involve just one nomination, of the Texas state judge Priscilla Owen to the 5th circuit court of appeals, based in New Orleans. Democrats claim she is an extreme conservative, unfitted to so important a post. Republicans contend that, whatever her views, she is entitled to a straight up-or-down vote. But they have only 55 of the 100 Senate seats, not enough to force an end to a filibuster.
Assuming this fate befalls Ms Owen, the Republican majority leader, Bill Frist, is expected to ask Vice-President Dick Cheney, in his role as Senate president, to declare filibusters illegal for federal appeal court and Supreme Court confirmation hearings. Mr Frist would then call a vote to uphold that ruling. This is the "nuclear option", so called because senators warn it will blow relations between the two parties to smithereens.
The Senate may stay in session throughout tonight, as Democrats have made plans to show, in a side room, Mr Smith Goes to Washington, the 1939 film in which Jimmy Stewart's character stages a 24-hour filibuster.
Though the immediate battle is over Ms Owen, and three other appeal court nominees, the real battle is for the Supreme Court. A critical referee in the culture wars over issues such as abortion and gay rights, it will have at least one, and perhaps three, vacancies to be filled by Mr Bush during his second term.
Chief Justice William Rehnquist, 80 years old and suffering from thyroid cancer, is likely to retire when the court's current term ends this summer.
Two other elderly Justices may also step down soon. Mr Bush meanwhile has terrified Democrats by saying that his model judges are Antonin Scalia and Clarence Thomas, the Supreme Court's most conservative members.
The filibuster struggle is thus colossally important. If the rules are changed, Democrats are expected to use other procedural devices to slow Senate business to a crawl, thus imperilling the President's entire legislative agenda, including social security and energy policy reform, and thus complicate the whole process of government.
Hopes for averting a showdown rest on what has been called the Gang of 12 - a group of moderate Senators, six of them Democrats and six Republicans.
Under a mooted deal, these Republicans would vote against the nuclear option. In return, the six Democrats would agree to use the filibuster only in extraordinary circumstances. The problem is what constitutes "extraordinary circumstances".
"A bipartisan compromise will be agreed to," predicted Joe Lieberman, a Connecticut Democrat and one of the 12. But even he conceded that other sticking points remain, and as the critical week began, the odds were that the effort would fail. It is generally believed that Mr Frist would not have opted for a showdown unless he had the votes. A mere 50 of the 55 Republican Senators will suffice, as Mr Cheney has said he would cast his tie-breaking vote in favour of the rule change.
The longest speeches
* 1919: The Senate votes to end a filibuster against ratification of the Treaty of Versailles that ended the First World War. However, the treaty was rejected.
* 1935: Huey Long, a Democrat from Louisiana, read fried-oyster recipes during a 15 1/2-hour attempt to keep federal jobs from his political enemies.
* 1957: Strom Thurmond, a South Carolina Democrat who became a Republican, made the longest speech in the Senate - 24 hours and 18 minutes against the Civil Rights Act of 1957.
* 1964: 18 Democrats maintained a 57-day filibuster against the Civil Rights Act of 1964. The Senate for the first time on a civil-rights issue voted to end the filibuster and the act was passed.
* 1968: Republicans led a filibuster against nomination from Democratic President Lyndon Johnson, right, to elevate Supreme Court Justice Abe Fortas to be chief justice.Reuse content